Field of the Invention
The present invention relates to a charger for vehicles, and more particularly, to a charger for vehicles capable of improving charging efficiency by reducing ripples of an output current of a direct current/direct current (DC/DC) converter.
Description of the Prior Art
Typically, a Phase Shift Full Bridge (PSEB) converter used in high power applications has a DC/DC converter, and enables zero voltage switching. However, when the PSPF converter is applied to a slow charger for an Electric Vehicle/Plug-in Hybrid Electric Vehicle (EV/PHEV) as shown in FIG. 1, the leakage inductance of the secondary side of a transformer T1 increases due to the step-up/down ratio of the input/output voltage of the PSFB converter being relatively low.
Due to the leakage inductance of the transformer T1 and a resonance phenomenon which occurs in the parasitic capacitance of the secondary side rectifier diode D6-D9, certain components are subjected to a surge voltage. For example, a snubber circuit is commonly used to absorb the energy generated using the resonance phenomenon and suppress a surge voltage applied to a device.
Conventionally, the DC/DC converter used in a charger for vehicles has a LC filter to facilitate mitigating the ripple current (e.g. charging energy) of the output capacitor C0 as shown in FIG. 1. However the ripple current magnitude of the output capacitor C0 is increased since the energy absorbed through the capacitor Cs1 of the snubber circuit charges the output capacitor C0 through the diode Ds2. Thus, the prior art has the disadvantage that an increased number of the output capacitors are required to facilitate suppressing the performance degradation and the ripple current. Additionally, a switching loss exists and the efficiency of the charger is reduced due to the freewheeling current of the transformer T1 being reduced in the OFF operation of a Field Effect Transistor switch due to the operating characteristics of a circuit.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.